关键词： solid polymer electrolyte   all-solid-state lithium battery   polyethylene oxide   conductivity   silica aerogel  

摘要： To improve the ionic conductivity and thermal stability of a polyethylene oxide (PEO)-ethylene carbonate (EC)-LiClO4-based solid polymer electrolyte for lithium-ion batteries, polymethyl methacrylate (PMMA) and silica aerogel were incorporated into the PEO matrix. The effects of the PEO:PMMA molar ratio and the amount of silica aerogel on the structure of the PEO-PMMA-LiClO4 solid polymer electrolyte were studied by X-ray diffraction, Fourier-transform infrared spectroscopy and alternating current (AC) impedance measurements. The solid polymer electrolyte with PEO:PMMA = 8:1 and 8 wt% silica aerogel exhibited the highest lithium-ion conductivity (1.35 x 10(-4) ***(-1) at 30 degrees C) and good mechanical stability. The enhanced amorphous character and high degree of dissociation of the LiClO4 salt were responsible for the high lithium-ion conductivity observed. Silica aerogels with a high specific surface area and mesoporosity could thus play an important role in the development of solid polymer electrolytes with improved structure and stability.

关键词： Lithium-ion batteries  

摘要： Extensive attention has been paid to metal-organic frameworks (MOFs) in the fields of gas storage/separation, sensors, catalysis, drug delivery and so on. However, the potential application of MOFs as electrolytes in lithium-ion batteries (LIBs) still needs to be further studied. In this study, showcased as the first example in the domain of all-solid-state electrolytes, a MOF covalently linked by flexible polymer chains toward a flexible stand-alone hybrid all-solid-state polymer electrolyte (HSPE) film is prepared by one-pot UV photopolymerization. Specifically, the precursors of the HSPE are composed of vinyl functionalized MOF (M-UiO-66-NH2) nanoparticles, poly(ethylene glycol) diacrylate (PEGDA), a lithium salt and a photoinitiator. It is confirmed that HSPE-1-8 (m(M-UiO-66-NH2):m(PEGDA) = 1:8) possesses over 5 times higher ionic conductivity (4.31 x 10(-5) S cm(-1) at 30 degrees C) and much better interfacial contact with Li electrodes than the SPE without incorporation of the vinyl functionalized MOF. Furthermore, at room temperature, the assembled cell of Li/HSPE-1-8/LiFePO4 exhibits outstanding rate capacity (it can reach 140, 124 and 80 mA h g(-1) at 0.2, 0.5 and 1C, respectively) and excellent long cycle performance. Meanwhile, the solid cell can also be well run at 60 degrees C (the discharge capacity reaches 110 mA h g(-1) at 2C). Combined with the superior low/high temperature performance of the cell, it is believed that the MOF-based hybrid SPE can be one of the most promising high-safety and high performance electrolytes for LIBs.

关键词： Ionic liquid-based gel polymer electrolyte   PVDF-HFP   Safety   Compatibility   Solid-state lithium battery  

摘要： Gel electrolyte is one of the most direct and appropriate ways to solve the safety problem of battery before the most challenging technological hurdles to all solid-state batteries have not yet been overcame. A major challenge towards gel polymer electrolyte (GPE) is making an electrolyte that is effectively combine with electrochemical performance, thermal safety and the stability to lithium. Here, PVDF-HFP-LiTFSI/SiO2/EMITTSI polymer electrolyte composite membrane (ILGPE) is prepared via solution casting method, in which nano-silica and ionic liquid positively effect on the performance of polymer electrolytes, such as ionic conductivity, electrochemical stability and thermal safety stability. It remarkably enhances the interface compatibility between ILGPEs and lithium metal. Significantly, we characteristically elucidate the possible transmission mechanism and interaction within the materials of ILGPE. Furthermore, Li/LiFePO4 battery based on such ILGPEs can exhibit fascinating interfacial stability and cycling performance. Herein, cells based on ILGPEs can overcome the drawbacks of solid electrolytes and volatile organic liquid electrolytes, which suggest a promising method for highly secure lithium batteries with appreciably enhanced performance.

关键词： Lithium compounds  

摘要： Here, novel solid polymer electrolytes were synthesized by solvent-free thiol-ene copolymerization with different chain lengths. It was demonstrated that the optimal polymer electrolyte exhibited excellent thermal stability up to 331 degrees C, considerable ionic conductivity of 5.05 x 10(-5) S cm(-1) at ambient temperature, a wide electrochemical window (0-5.05 V) and good compatibility with a lithium metal electrode. In addition, a solid-state monopolar LiFePO4//Li battery with an integrated cathode and electrolyte was assembled and delivered a maximum capacity of 167.39 mA h g(-1), which is close to the theoretical capacity of the LiFePO4 cathode. Moreover, the discharge capacity remained at 122.17 mA h g(-1) after 200 cycles at 60 degrees C, which represents a capacity retention of 75%. Remarkably, the monopolar cell could cycle well at room temperature, with a stabilized discharge capacity of 100 mA h g(-1) at 0.1C in the 60(th) cycle. In particular, taking advantage of the non-fluidity of solid electrolytes, a bipolar cell with a high voltage of 6.07 V was also assembled, which was extremely beneficial for improving the volumetric energy density and decreasing the cost, as well as enhancing the reliability of cell packs. The bipolar cell delivered an initial specific capacity of 136.3 mA h g(-1) with a retention of 76% after 40 cycles. Furthermore, the bipolar cell can work well under conditions of bending, cutting and even penetration by a nail. Consequently, this work provides an advanced strategy for the facile synthesis of polymer electrolytes, as well as the fabrication of bipolar cells with high voltages, which favors improvements in energy density.

关键词： Solid polymer electrolyte   Lithium battery   Polycarbonate   Polyurethane   All-solid-state  

摘要： Four kinds of polycarbonate-based polyurethane with 8-14 wt% hard segments content are synthesized via reactions of polycarbonatediol, hexamethylene diisocyanate and diethylene glycol. The mechanical strength of the polyurethanes increase with the increase of hard segments content. Solid polymer electrolytes composed of the polycarbonate-based polyurethanes and LiTFSI exhibits fascinating characteristics for all-solid-state lithium batteries with a high ionic conductivity of 1.12 x 10(-4) S cm(-1) at 80 degrees C, an electrochemical stability window up to 4.5 V (vs. Li+/Li), excellent mechanical strength and superior interfacial stability against lithium metal. The all-solid-state batteries using LiFePO4 cathode can deliver high discharge capacities (161, 158, 134 and 93 mAh g(-1) at varied rates of 0.2, 0.5, 1 and 2C) at 80 degrees C and excellent cycling performance (with 91% capacity retention after 600 cycles at 1 C). All the results indicate that such a polyurethane-based solid polymer electrolyte can be a promising candidate for all-solid-state lithium batteries.

关键词： In-situ preparation   Hybrid polymer electrolyte   Nanofiller   Good distribution   Positive effect   Solid-state lithium battery  

摘要： Nano-sized fillers in a polymer matrix with good distribution can play a positive role in improving polymer electrolytes in the aspects of ionic conductivity, mechanical property and electrochemical performance of Li-ion cells. Herein, polyethylene oxide (PEO)/Li3PS4 hybrid polymer electrolyte is prepared via a new in-situ approach. The ionic conductivities of the novel hybrid electrolytes with variable proportions are measured, and the optimal electrolyte of PEO-2%vol Li3PS4 presents a considerable ionic conductivity of 8.01 x 10(-4) S cm(-1) at 60 degrees C and an electrochemical window up to 5.1 V. The tests of DSC and EDXS reveal that the Li3PS4 nanoparticles with better distribution, as active fillers scattering in the PEO, exhibit a positive effect on the transference of lithium ion and electrochemical interfacial stabilities. Finally, the assembled solid-state LiFePO4/Li battery presents a decent cycling performance (80.9% retention rate after 325 cycles at 60 degrees C) and excellent rate capacities with 153, 143, 139 and 127 mAh g(-1) at the discharging rate of 0.1 C, 0.2 C, 0.5 C and 1 C at 60 degrees C. It is fully proved that it is an advanced strategy to preparing the new organic/inorganic hybrid electrolytes for lithium-ion batteries applications.

关键词： Polyethylene oxides  

摘要： A polyethylene oxide (PEO)-based composite solid polymer electrolyte filled with one-dimensional (1D) ceramic Li0.33La0.557TiO3 (LLTO) nanofibers was designed and prepared. It exhibits a high ionic conductivity of 2.4 x 10(-4) S cm(-1) at room temperature and a large electrochemical stability window of up to 5.0 V vs. Li/Li+, and is a promising electrolyte candidate for all solid-state lithium batteries.

关键词： 锂离子电池   聚合物电解质   全固态   聚氨酯   聚碳酸酯  

摘要： 传统的锂离子电池由于使用易挥发、易燃烧、易泄露的有机液态电解质,存在较大的安全隐患。使用固态聚合物电解质制备的全固态锂离子电池,能够避免液体电解质带来的安全问题,此外还具有能量密度高、加工成型简单等优点,成为当前锂电池研究领域的热点。围绕设计和开发新型固态聚合物电解质和全固态锂离子电池这一主题,本论文从聚氨酯的分子结构出发,通过设计不同的软硬段组成,制备了系列聚氨酯基固态聚合物电解质,并以聚氨酯为骨架,制备了聚氨酯基柔性正极膜和柔性全固态锂电池,为固态聚合物电解质和全固态锂离子电池的开发提供了新的思路。论文第一章介绍了锂离子电池的主要类型和固态聚合物电解质的离子导电机理,综述了固态聚合物电解质的基体和全固态锂电池的结构设计等方面的最新研究进展,提出了本论文的研究内容。论文第二章列出了本论文实验过程中使用的主要原料和仪器设备,介绍了实验过程中的测试方法。论文第三章以异氟尔酮二异氰酸酯、聚丙二醇、1,4-丁二醇和非离子聚醚二元醇为原料,合成了一种具有梳状结构的水性聚氨酯(NWPU),将NWPU与高氯酸锂(LiClO4)复合,制备了系列NWPU基固态聚合物电解质,研究了锂盐浓度对电解质性能的影响。研究表明,NWPU基电解质具有较好的力学性能和电化学稳定性,锂离子能够与聚氨酯软硬段络合,锂离子的传导主要发生在聚氨酯的软段区域,当LiClO4加入量为15 wt%时得到的NWPU基电解质综合性能最佳,在40℃和140℃时的离子电导率分别达到5.44×10-6 S cm-1和2.35×10-3Scm-1。论文第四章将第三章合成的NWPU和聚氧化乙烯(PEO)共混,并与双三氟甲基磺酰亚胺锂(LiTFSI)复合,制备了系列NWPU/PEO基复合固态聚合物电解质。研究表明,NWPU和PEO具有良好的相容性,NWPU作为聚合物骨架提高了 NWPU/PEO基复合固态聚合物电解质的力学性能和电化学稳定性,其中以NWPU与PEO质量比为1:3、LiTFSI加入量为30 wt%时制备的SPE2电解质综合性能最佳,拉伸强度达到1.3MPa,电化学窗口达到4.8 V,60℃时离子电导率达到8.2×10-4Scm-1。以SPE2组装的LiFePO4/SPE2/Li全固态电池在80℃、0.2C时放电比容量达到160 mAh g-1,1C循环100次容量保持率为96%。论文第五章以1,6-六亚甲基二异氰酸酯、聚碳酸酯二元醇和一缩二乙二醇为原料,合成了系列不同软硬段含量的聚碳酸酯型聚氨酯(PCPU),将PCPU与LiTFSI复合得到PCPU基固态聚合物电解质。研究表明,PCPU的拉伸强度随着硬段含量的增加而增大,最高可以达到23 MPa。以硬段含量为10 wt%、LiTFSI加入量为20 wt%制备的PCPU10-20%Li电解质综合性能最佳,60℃和80℃时的离子电导率分别达到1.58×10-5 S cm-1和1.12×10-4 S cm-1。以PCPU10-20%Li电解质组装的全固态锂电池在60℃和80℃时具有优异的循环性能。论文第六章通过相转化法以热塑性聚氨酯(TPU)、LiFePO4和导电炭黑(SP)为原料,制备了系列聚氨酯基柔性正极膜,研究了 TPU加入量对柔性正极膜性能的影响。研究表明,相转化得到的正极膜具有柔性和多孔性,且正极膜的孔隙率和吸液率随着TPU加入量的增加而增大,从而显著提高了柔性正极膜的倍率性能。论文第七章在第六章的基础上,将固态电解质浇铸在柔性多孔正极膜内部,得到正极/电解质一体化设计的柔性全固态锂电池,研究了溶剂加入量对正极膜形貌和柔性全固态电池性能的影响。研究表明,随着溶剂加入量的增大,正极膜内部会形成指状大孔,有利于电解质胶液的渗入,以复合电解质制备的柔性一体化固态电池具有较好的循环性能。论文第八章对全文进行了总结,提出了存在的问题和下一步的研究计划。

关键词： solid composite electrolyte   flexible membrane   ionic liquid   nonflammable   compatibility   ionic conductor  

摘要： Inorganic solid electrolytes (SEs) possess substantial safety and electrochemical stability, which make them as key components of safe rechargeable solid-state Li batteries with high energy density. However, complicated integrally molding process and poor wettability between SEs and active materials are the most challenging barriers for the application of SEs. In this regard, we explore composite SEs of the active ceramic Li1+xAlxGe2-x(PO4)(3) (LAGP) as the main medium for ion conduction and the polymer P(VDF-HFP) as a matrix. Meanwhile, for the first time, we choice high chemical, thermal, and electrochemical stability of ionic liquid swelled in polymer, which significantly ameliorate the interface in the cell. In addition, a reduced crystallinity degree of the polymer in the electrolyte can also be achieved. All of these lead to good ionic conductivity of the composite electrolyte (LPELCE), at the same time, good compatibility with the lithium electrode. Especially, high mechanical strength and stable solid electrolyte interphase which suppressed the growth of lithium dendrites and high thermal safety stability can also be observed. For further illustration, the solid-state lithium battery of LiFePO4/LPELCE/Li shows relatively satisfactory performance, indicating the promising potentials of using this type of electrolyte to develop high safety and high energy density solid-state lithium batteries.

关键词： All-solid-state lithium batteries   Composite electrolytes   Plastic crystal electrolyte   Electrical properties   Thermal properties  

摘要： All-solid-state lithium batteries using flexible solid electrolytes instead of combustible organic liquid electrolytes are the ultimate solution to address the safety problem of commercialized lithium ion batteries. In this study, a free-standing and thermostable polymer/plastic crystal composite electrolyte (PPCE) based on polymerized trimethylolpropane trimethacrylate (TMPTMA)-1, 6-hexanediol diacrylate (HDDA) matrix, and plastic crystal electrolyte was prepared for all-solid-state lithium batteries. The polymerized TMPTMA-HDDA-based matrix of a porous network structure coupled with plastic crystal electrolyte (PCE) in the pores reveals good compatibility. The as-synthesized PPCE possesses excellent flexible performance, thermostability, and high conductivity, showing that PPCE can reach 8.53 x 10(-4) S cm(-1) with 7.5 wt% monomers (PPCE-7.5%) at 25 A degrees C under a stability electrochemical window above 5.2 V. The assembled lithium batteries Li|PPCE|LiFePO4 exhibit high capacity and highly cycling stability at room temperature, indicating great potential of all-solid-state lithium batteries.